Grinding machine and method



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Nov. 28, 1944. A. K. SELNES I 2,363,559

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' GRINDING MACHINE AND METHOD I I Filed March 16. 1942 M v Jamm e/7* Afzrzlsiwz 6617286 Wei wi 5 4 9 s Ii WJVI/ h 0 2 .0 5 9 v M Nov. 28,1944. A. K. SELN ES 2,363,559

GRINDING MACHINE AND METHOD I Filed March 16, 1942 7' Sheets-Sheet I02Dresser Feed Backlash Compensaor Wheel Feed Or/f/cq Select/v39 fzvenz or7 Shee ts-Sheet Nov. 28, 1944. A. K. SELNES GRINDING MACHINE AND METHODFiled March 16, 1942 P m Km ow izverzzof iszfaiz allies ffi wvzga Nov.28, 1944. A. K. SELNE S GRINDING MACHINE AND METHOD Filed March 16, 1942Sheets-Sheet UNITED STATES PATENT OFFICE GRINDING MACHINE AND METHOD AlfKristian Selnes, Detroit, Mich, assignor to Ex-Cell-O Corporation,Detroit, Mich., a corporation of Michigan Application March 16, 1942,Serial No. 434,923

20 Claims. (Cl. 51-95) The present invention relates generally toimprovements in grinding machines and methods,

and has particular reference to grinding machines, such for example asthread grinders, in

In grinding certain types of work, such as screw elements, the workpieceis commonly translated axially in forward and return directionsrelatively across the cutting periphery of the grinding which both thegrinding wheel and the workpiece wheel, and often a grinding cut istaken in both are rotated and are relatively translated in fordirectionsof translation so as to avoid an idle reward and return directionsaxially of the workturn stroke and thereby to save time. For any piece,given direction and rate of relative translation,

I have found that, in the use of grinding mathe direction and speed ofrotation of the workchines of the foregoing character, the quality ofpiece is determined by the hand and lead of the surface finish that isobtained, and the rate at thread to be ground. Therefore, when gri whichthe stock can be removed without objecduring both forward and returnstrokes, t e work tionable results, is influenced by the direction of to t be reversed upon each reversal of rotation of the grinding wheelin'relation to the translation 0 that the grinding Wheel i fOllOWdirection of rotation of the workpiece. This re- .15 {the thread lead-This necessarily results in a lation is not always the same fordifferent workpieces to obtain the best operating performance andquality of machining. Workpieces of certain classes can be ground mostadvantageously while rotating the grinding wheel and the workpiece inopposite directions. The stock is thereby removed in a climb out inwhich the surfaces of the wheel and the workpiece travel in the samegeneral direction at the point of contact. Included in this category areworkpieces-having relatively small diameters, or containing tungsten, orhavin a high degree of hardness, such as edge cutting tools, orrequiring an uninterrupted cut, as in the relief grinding of taps.However, in grinding workpieces of other classes, such for example asaircraft cylinder barrels, and in general workpieces that have arelatively low degree of hardness or are relatively large in diameter,the best results are obtained by rotating the wheel and the workpiece inthe same direction to perform a conventional cut in which the surfacestravel in opposite directions at the point of contact. Moreparticularly, I have found that in grinding large workpieces atdesirable speeds and feeds, a climb out results in the exertion of aheavy pressure against the workpiece and attendant springing thereof, inthe generation of excessive heat, and

in objectionable discoloration of the ground surface due to burning,whereas a conventional cut permits the removal of the stock at acomparativelyhigh rate without causing discoloration and otherobjectionable results.

One of the objects of the present invention, therefore, is to provide anovel grinding machine wherein the direction of rotation of the grindingwheel relative to that of the work is subject to convenient selectivecontrol at the will T of the operator so that the grinding operationwill be performed in a manner best suited to the particular requirementsof each workpiece.

versal of the relative rotation between the grinding wheel and theworkpiece if the wheel is rotated constantly in one direction as inconven-- tional practice;

Another object of the present invention, therefore, is to provide anovel grinding machine and method of grinding in which a predeterminedrelative rotation between the grinding wheel and the workpiece ismaintained regardless of reversal of the work rotation.

A more particular object i to provide a novel thread grinding machineand method in which the rotation of the grinding wheel is automaticallyreversed upon reversal of translation and rotation of the workpiece.

p A further object is to provide a new and improved grinding machine ofthe foregoing character in which the workpiece is caused to dwell at theend of each cutting stroke to permit deceleration in the existingdirection and then acceleration to normal speed in the reverse directionof the grinding wheel before initiating the reverse cutting stroke.

Another object is to provide a novelgrinding machine and method in whichthe rotation of the grinding wheel is automatically reversed uponreversal of the work rotation while the wheel is out of contact with theworkpiece.

Further objects and advantages will become apparent as the descriptionproceeds.

In the accompanying drawings, 1 Figure 1 is a front elevational view ofa grinding machine embodying features of my invention.

Fig. 2 is a plan view of the machine.

Fig. 3 is a diagrammatic representation of the electrical driveandcontrol system used in the machine.

Fig. 4 is a front elevational view of a modified form of grindingmachine embodying the invention.

,Fig. is a detail view of the feed mechanism for the grinding wheel inthe machine of Fig. 4. Fig. 6 is a diagrammatic representation of thehydraulic system used in the machine of Fig. 4. Fig. 7 is a diagrammaticrepresentation of the electrical drive and control system used in the Imachine of Fig. 4.

Figs. 8 and 9 are diagrammatic views illustrating the method of theinvention respectively, with 1 the word and the grinding wheel rotatingin the same direction, and in opposite directions.

Machine structure bodiment, comprises a base It! supporting ahorizontally translatable work slide or table II. A headstock I2 ismounted on one end of the base I0, and includes a work drive shaft I3which is rotatably anchored at its outer end through a bearing bracketI4 to the table II and which is adapted to be rotated and simultaneouslytranslated axially in timed relation to the rotation to translate thetable II. Supported in the outer end of the shaft I3 is a live centerI5. A tailstock I6 is adjustably mounted on the table I I, and has adead center I1 in axial alinement with the 'center I5. The workpiece Wto be ground is rotat ably supported between the centers I5 and I1.

The drive for the work shaft I3 includes a reversible two-speed electricmotor I8 mounted on one side of the base I0, and connected through abelt I9 to mechanism (not shown) within the headstock I2 for rotatingthe shaft and for translating the shaft axially under the control of amaster lead screw (not shown). Upon rotation of the motor I8 in onedirection, the shaft I3 will be driven to translate the table II to theright in an initial or forward cutting stroke, and the workpiece W willbe rotated in a predetermined initial direction in timed relation to thetranslation as determined by the hand and lead of the screw thread to beground. Upon rotation of the motor I8 in-the opposite direction, thedrive to the shaft I3 will be reversed to trans-. late the table to theleft in a return stroke and to rotate the workpiece W in the reversedirection.

A grinding wheel assembl is mounted at the rear of the work table II ona cross slide 2[ supported on the base In for movement transversely ofthe axis of the workpiece W. The assembly 20 includes a spindle 22supporting a grinding wheel 23 and adapted to be driven through a belt24 from a reversible electric motor 25. The slide 2| is adapted to beoperatedby a feed mechanism (not shown) to advance the grinding wheelincrementally toward the work for successive cuts to the desired depth,and to quickly retract the wheelfrom the work, if desired, at the end ofeach cutting stroke. The feed mechanism includes a hand wheel 26 and aretract lever 21 for controlling the setting of the grinding wheel, anda wheel 28 for controlling the size setting.

Coolant from a tank 29 is adapted to be supplied, by a pump 30 through aduct 3| to the grinding zone. The pump is driven by an electric motor32.

The various motors I8, 25 and 32 are connected in an electric system andare adapted to be operated in a predetermined manner to obtain anautomatic machine cycle. A number of manually operable switches areincluded in the electrical control, and are mounted on a panel 33adjacent the operator's station at the front of the machine.

Electrical control circuits and operation Current is supplied for thevarious electric mo:

,tors I8, 25 and 32 from three main supply lines L1, L2 and L3 adaptedto be connected to a suitable source of three-phase alternating current.

Two low voltage supply lines L4 and L5 for the control circuits properare connected through a transformer 40 to the lines L1 and L3.

The coolant pump motor 32 is adapted to be connected to the main supplylines L1, L2 and L: by a starter having a set of normally open contactsP1 adapted to be closed upon excitation of a relay coil P.

The wheel drive motor 25 is adapted to be connected to the main supplylines L1, L2 and L3, to rotate the spindle 22 selectively in eitherdirection, by a starter having two parallel sets of normally opencontacts GFi and GR/l adapted to be alternately closed respectively uponselective excitation'of relay coils GF and GR.- Thus, when the coil GFis excited, the motor 25 will rotate in a forward direction, and whenthe coil GR isv open contacts WF1 and WR]. adapted to be alternatelyclosed upon selective excitation ofrelay coils WF and WR to translateand rotate the workpiece W alternately in forward and reversedirections. The starter also includes two additional parallel sets ofnormally open contacts S1 and F1 connected in series with the directioncon-'- trol contacts W1 and WRl, and adapted to be closed selectively tocontrol the speed of the motor I8. The contacts Si and F1 are controlledrespectively by two relay coils S and F adapted to be connectedselectively across the supply lines L and L5 under the control of twoselector switches S2 and S3 and upon closing either of two contacts WF:and WR2 under the control of the coils WF and WR. When the coil WF isexcited, the contacts WFz will close a circuit through the switch S2either for the coil S or the coil F depending on the adjustment of theswitch. Similarly, when the coil WR is excited, the contacts WRz willclose a circuit through the switch S3 either for the coil S or the coilF depending on the adjustment of this switch. Consequently, by selectiveadjustment, the motor I8 can be driven at either slow or fast speed ineither direction as desired. Where a grinding out is taken in bothdirections of work translation, both switches S2 and S3 are adjusted toclose the circuit for the coil S, and the coil F is never excited, sothat the motor I8 is driven at a slow speed in both directions ofrotation.

The rotation of the motors I8 and 2-5 is adapted to be reversedautomatically at each endof the work translation. The direction ofrotation is under the control of atwo-position limit switch 151 adaptedfor actuation by the table II alternately into opposite stations. Duringthe forward movement of the table II, the limit switch LS1 serves tocomplete a circuit across the supply lines L4 and L5 for a relay coil U.During the reverse direction, the limit switch 1S1 serves to complete acircuit for a relay coil L. The relay coils U and L form part of a latchrelay LR which controls contacts LR1 and LR: in the circuits for thecoils GF and GR and contacts LR: and LE4 in the circuits for the coilsWI? and WR. When the coil U is excited, the contacts LRi and LR: areclosed and the contacts LR: and LR4 are opened. When the coil L isexcited, the contacts LRi and LR: are opened and the'contacts LR: andLR4 are closed. The contacts remain closed in each instance even thoughthe coil in control thereof is deenergized by opening the switch LS1until the companion coil of the relay LR is energized.

Excitation of the coils P, GF and GR is under the control of a normallyopen starting push button switch S and a normally closed stopping pushbutton switch S5. Interposed in the circuits for the coils GF and GR, inseries with th contacts LR1 and LR: is a manual selector switch So whichis adjustable to control the rotation of the grinding wheel 23 inrelation to the rotation of the workpiece W. The switch S6 is availableto reverse the connections of the coils GF and GR in the circuits, sothat in one station of theswitch the grinding wheel and the workpiecewill rotate in the sam direction as illustrated in Fig. 8 to perform aconventional cut, and in the other station of the switch the wheel andthe work will rotate in opposite directions as shown in Fig. 9 toperform a climb out. If the master lead screw in the headstock l2 should,be changed so as to have an opposite hand lead, it would be necessaryto reverse the position of the switch S6 in order to retain the desiredrelative rotation between the wheel and the workpiece.

Also interposed in the circuits for the coils GF and GR is a manualselector switch S? which in the station shown serves to place the coilsunder the selective control of the limit switch LS1, and which, ifadjusted into the opposed station, would connect the coil GF across theswitch S5 to effect rotation of the grinding wheel 23 constantly in onedirection regardless of reversal of the table I l and reversal ofrotation of the workpiece W at each end of the table travel.

Assuming that the switch S1 is adjusted to condition the system forautomatic reversal of the grinding wheel upon reversal of the workrotation, and that the switch S6 isadjusted to establish the desireddirection of rotation of the wheel in relation to that of the work,operation is instituted by momentarily closing the switch S4. Thiscompletes a circuit'for the coil P from the supply line L4 through thcoil P, a line 4|, the switch S4, a line 42, the switch S5, and a line43 to the supply line L5. Interposed in the line 43 is a master stopswitch S8 and a plurality of overload contacts 44. Excitation of thecoil P serves to close the contacts P1 to institute'operation of thecoolant motor 32, and also to close contacts P2 to establish a holdingcircuit across the switch S4.

With the limit switch 181 in the position shown, the contacts LRi areclosed and the contacts LR: are opened. Consequently, closing of theswitch S4 serves also to establish a circuit for the coil GF from thesupply line L; through the coil, a line 45, the switch $6, a. line 46,the contacts LRi, a line 41, and the switch S1 to the line 4|. Exci- GFito institute rotation of the wheel drive motor in a forward direction.If the switch S6 had been adjusted into the opposed sation, the coil GRinstead of the coil GF would have been energized to institute rotationof the motor 25 initially in the reverse direction, the circuit leadingfrom the supply line L4 through the coil GR, a line 48, and the switchS6 to the line 46. If the switch S1 had been adjusted into the opposedstation, the circuit for the coil GF would have been completed from theline 45 through a shunt line49 across the switch S6 to the line 4|.

Upon reversal of the-switch LS1 at the end of the table movement in theforward direction, the coil U is deenergized and the coil L isenergized, thereby opening the contacts LRi' to interrupt the circuitfor the 'coil GF and closing the contacts LR: to establishthe circuitfor the coil GR. Excitation of the coil GR serves to close the startercontacts GR1, thereby reversing the direction of rotation of the motor25 and consequently-the rotation of the grinding vwheel 23.

Operation of the motor 18 for translatin and rotating the workpiece Wreversibly is instituted by momentarily closing a manual switch S9. Thisthe line 50. Excitation of the coil RA serves to close contacts RA1 tocomplete a holding circuit for the coils TR and RA across the switch S9.

The contacts RD and RE1 are adapted to be opened respectively uponexcitation of two relay coils RD and RE.

Excitation of the timing relay TR serves to close a switch TRi, therebyconnecting a line 52 from the starter coils WF and WR to the line 43.

I Two normally open contacts RD2 and REz are LRa, the line 52 and theswitch TR1 to the line tation of the coil GF serves to close thecontacts 75 connected in series in a shunt line 53 across the switchTRl. Since the contacts LRa are closed,

the switch TRi will complete a circuit for the coil WF from the supplyline L4, through the coil, normally closed interlock contacts WR:controlled by the coil WR, a line 54, the contacts 43. The coil RD,being connected in parallel with the coil WF, is also excited, and opensthe contacts RDi'and closes contacts RDz and RDa. Excitation of the coilWF serves to open interlock contacts WFa in the circuit for the coil WR,and

to close the contacts WF1 and WF2. Closing of the contacts WFz serves toeffect excitation of the coil S to close the contacts S1. Consequently,operation of the motor [8 is instituted to rotate the workpiece W in aforward direction, as indicated by the full line arrow in Figs. 8 and 9,and to advance the table II in a forward direction. The grinding wheel23 is also rotated in a forward direction, as indicated by the full linearrow in Fig. 8, so that the wheel and the. work are rotated in the samedirection and hence are moving oppositely at the point of contact toproduce a conventional cut.

During the forward operation of the motor l8,

a plugging switch 55 is actuated to open contacts PR and to closecontacts PF. This establishes a circuit for the coilRE from the supplyline L4 through the coil, a line 56, normally open contacts WF4 whichare closed at this time by the coil WF, and the contacts PF to 'thesupply line L5. The coil RE serves to close contacts RE:

across the contacts WF4'; also, to open the contacts RE1 and to closethe contacts REz. Consequently at this time, the coil TR is deenergizedsince the contacts RDi and REl are both open, and causes the switch TRito open. However, the starter circuit is maintained since the contactsRD: and R132 are both closed across the switch TRi.

At the end of the forward cut, the switch LS1 is actuated by the tableII to interrupt the circuit for the coil U and to complete the circuitfor the coil L, 'of the latch relay LR. As a result, the contacts LRlare opened and the contacts LR2 are closed to effect reversal of themotor 25 so as to rotate the grinding wheel 23 in the directionindicated by the dotted arrow in Fig. 8. At the same time, the contactsLR; are opened to break the circuit for the starter coil WF, therebyeife'cting opening of the contacts WFi-and WFz to interrupt the forwarddrive motor circuit. The circuit for the coil RD also is broken so thatthe contacts RDi are again closed and the contacts RDz are opened. Thecontacts LRA also are closed to condition the circuit for the coil WRfrom the line L4 through the coil, the contacts WFa which are nowclosed, the line 56, and the contacts LR4 to the line 52, but thecircuit is not completed to the line 43 since the contacts RD2 are open.However, a plugging circuit for the coil WR is completed from the lineL4 through the coil, the contacts WFa, the line 56, the contacts REs,and the plugging contacts PF to the line L5. Excitation of the coil WRserves to close the contacts WRI and WRz, and the coil break thecontacts PF, thereby interrupting the exciting circuit for the coils REand WR. De-

energization of the coil RE'opens the contacts REz and recloses thecontacts REi.

Since both contacts RDi and REI are again closed, the circuit throughthe starting relay TR is reestablished across the manual starting switchS9 since the coil RA has not been deenergized and has maintained thesealing circuit throughthe contacts RA1. Excitation of the timing relayTR again closes the switch "R1 to establish this time a circuit for thecoil WR through the contacts LR4. Excitation of the coil WR serves toopen the interlock contacts We in the circuit for the coil WF and toclose the contacts WRi and WRz, thereby establishing the reverse drivecircuit for the motor I8. The coil RE, being connected in parallel withthe coil WR through the line 56, is also excited and serves to close thecontacts RE2 and RE3 and to open the contacts RE]. During reverseoperation, the plugging contacts PR are closed to complete a circuit forthe coil RD through the contacts WR4. Excitation of the coil RD servesto close the contacts RDz and BBQ and to open the contacts RD1. Sincethe contacts R131 and REl are now both open, the coil TR is deenergizedto open the switch TRI, but the circuit for the coils RE and WR ismaintained through the contacts RD2 and RE2.

A cutting stroke is now obtained during the rei for' another cut in theforward direction, orthe turn movement of the slide H. During this re-75 operation can be stopped by opening the switch It will be noted thatat each end of the table travel, the reversal of the table drive isdelayed to provide a dwell during which the grinding wheel 23 isdecelerated in the prevailing direction of rotation, and thenaccelerated to full speed in the opposed direction of rotation. In otherwords, the workpiece W is not translated while reversal of the grindingwheel 23 is being effected.

In some instances, it may be desirable to leave the grinding wheel incontact with the work while efiecting reversal so as to loosen anyglazed grains and to sharpen the surface of the wheel. However; in otherinstances, it is preferable to effect reversal of the grinding wheel 23while out of contact with or retracted from the workpiece W. To thisend, a solenoid RC is adapted to be connected across the main supplylines 1 and L3 by two contacts RB1 and RB: under the control of a relaycoil RB connected across the lines L4 and 52. When the starting circuitfor either of the coils W? and WR is established across the switch TR1,the coil RB will be excited to close the contacts RBi and BB2. As aresult, the solenoid RC will be actuated to advance the grinding wheel23 into operative position. Upon interrupting the circuit from the line52 to the line 43 at each end of the table travel, the coil RB isdeenergized to open the contacts RBI and RBz. Thereupon, the solenoid RCis disconnected to effect retraction of the grinding wheel 23 from theworkpiece W and it is in this retracted position that the rotation ofthe grinding wheel is reversed.

Hydraulic machine structure work, and has a combined hydraulic andelectric control. Apart from the specific control, the machine issubstantially like that disclosed in United States Letters Patent No.2,251,961. issued August 12, 1941, to Ira J. Snader, to Which referencemay be had for a more detailed understanding of the mechanicalstructure.

Referr'ng to Figs. 4 and 5, the machine comprises a base 60, and a worktable 6| reciprocable thereon. A headstock 62 is supported on one end ofthe table 6|, and encloses a work spindle 63 having a live center 64.Adjustably mounted on the table 6| in spaced relation to the headstock62 is a tailstock 65 having a-dead center 66 in axial alinement with thecenter 64. It will be understood that the workpiece (not shown) isadapted to be operably supported by the centers 64 and 66.

The work spindle 63 is adapted to be driven by a reversible, variablespeed rotary hydraulic motor 61 mounted within the headstock 62andconnected through a belt 68 to a mechanical drive mechanism 69. Thework table 6| is adapted to be translated in opposite directions and intimed relation to the rotation of the spindle 63 by a nut and screwdrive (not shown) within the base and connected to the spindle drivemechanism It. Pressure fluid for operating the motor 01 is supplied by apump I0 mounted at the rear of the base 60, and driven by an electricmotor 1 I One end of the nut and screw drive for the table 6| isconnected to a backlash compensator I2 having a hydraulic cylinder I3and an actuating piston I4 anchored to a shaft extension 15 of thescrew,

Mounted on the rear of the base 60 is a grinding wheel assembly I6including a spindle structure I'I driven by a reversible electric motor18 and supportin a grinding wheel 79. The spindle structure 11 ismounted on a cradle 80 on a cross slide (not shown) movable toward theworkpiece to feed the grinding wheel 10 step by step into the work tofinal depth in timed relation to successive cutting strokes of the table6|. The cross feed is actuated a predetermined distance at each reversalof the table 6|, and includes a feed screw 8| operatively connected tothe cross slide and provided with a hand wheel 82.

A hydraulic feed mechanism is provided for automatically actuating thescrew 8i. In the present instance, the feed mechanism (see Fig. isoperated by a hydraulic actuator 83 having a cylinder 84 inwhich adouble end piston 85 is 'reciprocable. The piston 85 is formedintermediate its ends with a longitudinal gear rack 86 meshing with apinion 81 and adapted in each stroke to rotate the latter through onecomplete revo-' lution. A disk 08 is fixed for rotation with the pinion81, and carries an eccentric crank pin 89 connected to one end of anadjustable rod 90. The other end of the rod 90 is formed with a gearrack 9| meshing with a pinion 92 in turn in engagement with a gearsegment 93. A feed pawl 94 is revolvable'with the segment 93, and isarranged for engagement with a ratchet 95 operatively connected to thecross feed screw ill. The depth of cut during each grinding stroke iscontrolled by an adjustable shield 95 arranged to lift the pawl from theratchet 95 during a portion of each pawl stroke.

Associated with the cross feed mechanism is a hydraulic actuator 91available to locate the grinding wheel 19 in operative position duringthe grinding cut, and on occasion to retract the wheel from the work.The actuator 91 comprises a cylinder 98 enclosing a reciprocator piston99.

Associated with the grinding wheel I9 is a suitable dressing mechanismhaving one or more tools (not shown) movable by a reversible electricmotor I00 back and forth in a dressing cycle across, the cuttingperiphery of the grinding wheel 19, and having a hydraulic actuator'IIlI for advancing the tools toward the wheel in a dressing feed. Theactuator IOI comprises a cylinder I02 and an operating" piston I03reciprocaole therein.

Coolant is adapted to be supplied to the grinding zone through a ductI04 from a pump not shown) driven by an electric motor I05.

. Hydraulic system The machine comprises a hydraulic control.

The pump 10 has an inlet line Illltaking fluid from a supply tank I01,and has a pressure delivery line I08 connected to a main control valveI09 for the hydraulic motor 61. The pump 10 is of the variable deliverytype, such for example as disclosed in a copending application SerialNo. 147,178 filed June 9, 1937, by Ira J. Snader and Max-A. Mathys, andhas a volume control line IIO for varying the displacement in accordancewith the requirements of the motor Bl.

The main valve I09 is of the three-position t pe, and has a plunger IIInormally urged by spring pressure into the intermediate position. Theends of the valve plunger III are operatively connected respectively totwo operating solenoids S01 and S02. Upon excitation of the solenoid801, the plunger III will be shifted into the left end position toconnect the pressure line I08 to a line II 2 leading to one side of thehydraulic motor 61 and to connect a line I I3 from the other I side ofthe motor to an exhaust line II4. Upon excitation of the solenoid S02,the plunger III will be shifted into the opposite end position toreverse the connections for the lines II?! and II 3, thereby effectingreversal of the motor 61. In the neutral position, which obtains whenboth solenoids are deenergized, the plunger II I blocks both lines 2 andI I3 to stop the motor 61. The valve plunger III also serves when ineither end position to connect the pump control line IIO to the exhaustline H4, and when in neutral position to connect the control linethrough a passage I I5 to the pressure line I 08;. When the exhaustpressure is relatively low, the pump I0 will deliver a correspondinglylarge volumeof fluid to operate the motor 61 at a rapid rate. When theexhaust pressure is relatively high, the pump 10 will deliver acorrespondingly small volume of fluid to operate the motor 61 at a slowrate. When the pressure line I08 is connected to the control line IIO,the pump delivery is at a minimum and merely enough to maintain thenormal working pressure.

The displacement of the pump 10, and hence the operating speed of themotor 61., therefore is under the control of the exhaust pressure. Toeffect desired variations in the operating speed of the hydraulic motor61, a plurality of adjus able restricted flow orifices H6, H1 and H8,discharging through a drain line II9 to the tank I01, are arranged forselective connection with.

the exhaust line II4 under the control of an orifice selection valveI20.

The orifice selection valve I20 comprises a shiftable three-positionplunger I2I operatively connected at opposite ends respectively to twoactuating solenoids S03 and S04, and normally urged into neutralposition by spring pressure. In the neutral position of the plunger IZI,the exhaust line H4 is connected through a passage I22 in the plunger tothe orifice III. Upon excitation of the solenoid S03, the plunger I2I isshifted into the left end position to connect the exhaust line II4 tothe orifice 6. Upon excitation of the solenoid S04, the plunger I2I isshifted into the right end position to connect the exhaust line I I4 tothe orifice II8. By selective adjustment of the orifice restrictions,different back pressures can be obtained in the exhaust line II4 so thatthe work table Bl can be. translated, for example,

with a rapid approach, a slow cutting rate in one direction, and thesame or a different slow cutting rate in the opposite direction.

A series of auxiliary controlvalves I23, I24,

I25 and I26 are provided for respectively controlling the actuators I2,63, 91 and IN. Each of these valves has a pressure connection with anauxiliary pressure line I21 supplied with fluid through a pressurereducing valve I28 from the main pressure line I08. The. valve I28 isoperative to maintain a substantially constant predetermined lowpressure in the line IZ'L I n the event of a pressure drop in the lineI21, the valve I28 will admit additional make-up fluid thereto from theline I08. In the event of a pressure rise in the line I21, the valve I28will spill excess fluid therefrom to the drain line H9. The backlashcompensator valve I23 is of the two-position type, and has a plunger I29connected at opposite ends respectively to two actuating solenoids S and$06. In one position,

the plunger I29 will connect the pressure line I2'I through a line I30to one end of the cylinder I3. In the other end position, the plungerI29 will connect the line I21 through a line I3I to the other end of thecylinder I3. In each posi- 9 tion of the valve I23, the line receivingfluid displaced by the piston 14 is connected to the drain line II9.

The wheel feed control valve I24 is also of the two-position type, andhas a plunger I32 connected at opposite ends respectively to twoactuating solenoids S01 and S09. Upon excitation of the solenoid S01,the plunger I32 will be shifted into one end position to connect thepressure line I21 through a line I33 to one end of the wheel feedcylinder 84 and to connect the other end of the cylinder through a lineI34 to the drain line II9. Upon excitation of the solenoid S08, the

connections for the lines I33 and I34 will be reversed.

The retract valve I.25 is of the two-position type, and has a plungerI35 normally located ina stop position by a spring I36 to connect thepressure line I2'I through a line I31 to one end of the retract cylinder98, and to connect the other end of the cylinder through a line I38 tothe drain line H9. The plunger I35 is connected to an actuating solenoidS09 which, when energized, will shift the plunger against the action ofthe spring I 36 to reverse the connections for the lines I31 and I 38.When the solenoid S09 is energized, the grinding wheel I9 is advancedinto cutting position, and when the solenoid is deenergized, the wheelis retracted from the work.

The dresser feed valve I26 is similar to the valve I25, and comprises aplunger I39 normally held in a stop position by a spring I40 to connectthe pressure line I21 through a line I4I to one end of the dresser feedcylinder I02, and to connect the other end of the cylinder through aline I42 to the drain line H9. The plunger I39 is connected to anactuating solenoid S019 which when energized will shift the plunger toreverse the connections for the lines MI and I42.

Electrical control circuits and operation The grinding wheel motor I8and the coolant pump motor I05 correspond to the motors 25 and 32 ofFig, 3. These motors of the two machines across the switch SwI.

over a master stop switch Sw2. Energization of the coil H serves toclose holding contacts H2 The contacts H. are located in the line L5 sothat if the pump motor II is not conditioned for operation, the entiresystem is disabled.

To institute the machine cycle, a manual switch S103 is closedmomentarily to connect'a relay coil C over the normally closed stopswitch S204 across the main supply lines L4 and L5. Excitation of the,

coil C closes contacts C1, C2 and C3. The contacts C2 serve to connect arelay coil D over limit switch LS5 across the supply lines L4 and L5.Excitation of the coil D closes contacts D1, D2 and D3 and openscontacts D4 and D5. Contacts C1 and D1 establish a holding circuitacross the switch Sw3 for the coils C and D, and the contacts D2establish an additional holding circuit across the contacts C2 for thecoil D.

Since contacts U1 have been closed by the coil U, while contacts L1remain open, closing of the contacts Ca and D3 serves to connect thesolenoid S01 across the supply lines L4 and L5, thereby adjusting thevalve I24 to impart a forward feed to the grinding wheel. If the coil Lhas been energized instead of the coil U, the solenoid S09 would havebeen energized by closing the con-' tacts L1 to efiect the approachfeed.

The retract solenoid S09 is adapted to be connected in parallel with theselected one of the starting solenoids S01 and S0: for the hydraulicmotor 61. A selector switch Sw5 is adjustable to effect energization ofthe solenoid S09 either during the forward travel or during the returntravel of the work table, or during the travel of the table in bothdirections, with merely a temporary tool retraction at the end of eachstroke. The switch Sw5 controls the connection of the solenoid S09through two parallel contacts U2 and U9 adapted to be actuated by thecoil U. The contacts U2 are normally open and the contacts U3 arenormally closed. In one adjustment of the switch Sw5, both of thesecontacts are interposed in the circuit so that the solenoid S09 will beenergized regardless of whether or not the coil U is energized ordeenergized. In another adjustment of the switch 3105, only the contactsU: are interposed in the circuit, and in this event the solenoid S9 isdeenergized during the forward travel and energized during the returntravel of the table. In a third adjustment of the switch Sw5, only thecontacts U2 are interposed in the circuit, and in thisevent the solenoidS09 is energized during the forward travel and deenergized during thereturn travel of the table.

At the end of the cross feed movement, a cam lobe I43 on the disk 88(Fig. 5) serves to close a limit switch LS4, thereby completing acircuit for a relay coil E and the solenoids S01 and $06, from the lineL4 through interlock contacts F1, the contacts U4 now closed by the coilU, and the switch LS4 to the line L5. Simultaneously; the

circuit is closed for the retract solenoid S09 to tion-valve I20 isadjusted to connect the orifice v I I6 in the exhaust line I I4.

At the end of the approach, the table 6| closes a limit switch LS9 toenergize a relay coil G. Ex-

asoaue drive means for rotating said spindles, said drive citation ofthe coil G serves to close contacts (31 in the circuit for the solenoidS02, and to open the contacts G2, thereby. eifecting adjustment of thevalve I20 into neutral to connect the feed orifice H1 in the exhaustline H4. The motor 61 now operates in the forward direction at arelatively low feed rate in accordance with the setting of the orifice.

.At the end of the grinding stroke in the forward direction, the limitswitch LSris actuated to effect deenergization of the relay coil U andenergization of the relay 0011 L. 'I'hereupon, the contacts U1, U2, U4are opened, and the contacts U3 and L1 to L4 are closed. This closes acircuit for the coil F and the solenoids S02 and $05, from the line L;through interlock contacts E1, contacts L2 and contacts G1 to theswitch. LS4.

, Excitation of the solenoid S02 serves to reverse the valve I09 toreverse the direction of rotation of the motor 61, and excitation of thesolenoid S05 serves to reverse the valve l23to re verse the backlashcompensator. Also, the solenoid S07 is deenergized and the solenoid SOais energized to impart a forward feed increment to the grinding wheel.Upon initiation of the feed increment, the limit switch LS4 is opened tointerrupt the reversal of the table 6| until the feed movement iscompleted. During the dwell occasioned by the wheel feed. the solenoidS09 is deenergized to retract the wheel and the wheel motor I8 isreversed.

The grinding wheel may be dressed at any convenient time. To start thedressing operation, the hand switch SwB is closed, thereby completing acircuit for the solenoid S010 and the relay coil K through the normallyclosed stopswitch Sw'l.

The solenoid SO10 actuates the valve I26 to impart a forward feed ofthe'dressing mechanism toward the grinding wheel. The'ccil K closesholding contacts K1 across the switch SwB.

Atthe, end of the dresser feed, a limit switch LS3 is closed to completea circuit for a coil DF, from the main line L; through limit switch LS6,the coil DF, normally closed interlock contacts DB2, the switch LS3, andthe switch Swl to the main line L5. Excitation of the coil DF serves toclose starter contacts DF1 in the circuits for the dresser motor lllll,thereby energizing a brake solenoid I to release the motor brake andcausing the motor to operate in a forward direction. At the end of theforward movement, the limit switch LS6 is opened. and the limit switchLS1 is means including control means for reversing the rotation of saidgrinding spindle, whereby said grinding wheel may be caused to rotateselectively in either the same or opposite direction relative to therotation of the workpiece.

2. A grinding machine comprising, in combination, means including a workspindle for supporting a workpiece for rotation about afixed axis, drivemeans operable to rotate the workpiece selectively in either direction,means for upporting said spindle for translation in timed closed todeenergize the coil DF and energize a coil DR. The coil DR openscontacts DR: to open the circuit for the solenoid SO10 so as to impartan additional dresser feed, and closes the motor contacts DRl to reversethe rotation of the dresser motor. I00. At the end of the cycle, theswitch S101 is opened to interrupt the dressing operation.

The work table continues to reciprocate back and forth to takesuccessive grinding cut-s until the work is ground to the desired depth.Thereeral cutting engagement with the workpiece, and II relation to thespindle rotation, a grinding spindle having a rotary grinding wheelarranged for peripheral cutting engagement with the workpiece, drivemeans for rotating said grinding spindle, and control means forautomatically reversing said lastmentioned drive means to effectreversal of the rotation of said grinding spindle upon reversal of thetranslation and rotation of said work spindle, said control meansincluding selector mean-s for determining the direction of rotation ofsaid grinding spindle relative to the direction of rotation of said workspindle.

3. A grinding machine comprising, in combination, means including a workspindle for supporting a workpiece for rotation about a predeterminedaxis, drive means for rotating said workpiece selectively in eitherdirection, means for supporting said spindle for translation in timedrelation to the spindle rotation, a grinding spindle having a grindingwheel mounted for peripheral cutting engagement with the workpiece,reversible drive means for rotating said grinding spindle, and controlmeans selectively adjustable to effect rotation of said grinding wheelconstantly in one direction or the other or to efiect automatic reversalof the rotation of said grinding wheel upon reversal of the translationand rotation of the workpiece.

4. A grinding machine comprising, in combination, means supporting aworkpiece for'rotation,'drive means for rotating said workpieceselectively in either direction, a grinding spindle having a grindingwheel mounted for cutting en-.

gagement with the workpiece, reversible drive means for rotating saidspindle, and control means selectively adjustable to effect rotation ofsaid grinding wheel in one direction or the other relative to therotation of the workpiece, and operable to effect automatic reversal ofthe rotation of said grinding, wheel upon reversal of the rotation ofthe workpiece. I

5. A method of grinding rotary workpieces with a rotary grinding wheelwhich consists in positively rotating the workpiece in a predeterminedinitial direction and simultaneously rotating the grinding wheel in apredetermined initial direction relative to the workpiece with saidgrinding wheel and workpiece in peripheral cutting engagement.translating said workpiece axially in a given direction in timedrelation to the rotation of said workpiece, reversing the translationand rotation of the workpiece, and automatically reversing the rotationof the grinding wheel upon reversal of rotation of the workpiece,whereby to maintain the preselected rotary cutting relationially in agiven direction in timed relation to the rotation of said workpiece,reversing the translation and rotation of'the workpiece, andautomatically reversing the rotation of the grinding wheel upon reversalof rotation of the workpiece, whereby to maintain the preselected rotarycutting relationship between said wheel and the workpiece.

7. A method of grinding rotary workpieces with a rotary grinding wheelwhich consists in positively rotating the workpiece in a predeterminedinitial direction and simultaneously rotating the grinding wheel in adirection opposite to the rotation of the workpiece with said grindingwheel and workpiece in peripheral cutting engagement, translating saidworkpiece axially in a given direction in timed relation to the rotationof said workpiece, reversing the translation and rotation of theworkpiece, and automatically reversing the rotation of the grindingwheel upon reversal of rotation of the workpiece, whereby to maintainthe preselected rotary cutting relationship between said wheel and theworkpiece.

8. A grinding machine comprising, in combination, a base, a spindlemounted on said base and supporting a rotary grinding wheel, areversible electric motor for driving said spindle, a work table forsupporting a rotary workpiece and mounted on said base for reciprocationaxially of the workpiece through cutting engagement with the grindingwheel, means including a reversible electric motor for translating saidtable and for rotating the workpiece in timed relation to thetranslation, and electric control means operable by said table at oneend of said translation to efiect reversal of both of said motors,whereby to maintain a preselected relative rotation between saidgrinding wheel and the workpiece during rotation of the workpiece in theinitial direction and subsequent rotation of the workpiece in thereverse direction respectively for the forward and return cuttingstrokes of said table.

9. A grinding machine comprising, in combione direction or the otherrelative to the direction nation, a base, a spindle mounted on said baseand supporting a rotary grinding wheel, a reversible drive means forsaid spindle, a work table for supporting a rotary workpiece and mountedon said base for reciprocation axially of the workpiece through cuttingengagement With the grind ing wheel, reversible drive means fortranslating said table and for rotating the workpiecein timed relationto the translation, and control means operable by said table at one endof said translation to efiect reversal of both of said drive means,whereby to maintain a preselected relative rotation between saidgrinding wheel and the workpiece during rotation of the workpiece in theinitial direction and subsequent rotation of the workpiece in thereverse direction respectively for the forward and return cuttingstrokes of said table.

10. A grinding machine comprising, in combination, means for supportinga workpiece for timed rotation and translation in forward and returndirections, a spindle supporting a grinding wheel mounted for cuttingengagement with said workpiece, and means automatically operable upontranslation of said workpiece into a predetermined position to effectconcurrent reversal in the rotation of the workpiece and said grindingwheel.

ll. A'grinding machine'comprising, in combination, means supporting aworkpiece for rotation and for translation in timed relation to therotation, drive means for said workpiece automatically operable toeffect reversal of said translation of rotation of the workpiece andoperable to maintain the preselected relative rotation betweensaidgrinding wheel and the workpiece regardless of reversal of rotationof the workpiece.

12. A grinding machine comprising, in combination, means supporting aworkpiece for rotation and for translallon in timed relation to therotation, drive means for said workpiece automatically operable at apredetermined point in said translation to effect reversal of saidtranslation after a. dwell period and a reversal of rotation of theworkpiece during said period, a grinding spindle supporting a grindingwheel for cutting engagement with the workpiece in both directions oftranslation of the workpiece, drive means for rotating said spindle, andcontrol means for said last mentioned drive means automatically operableduring said dwell period to effect reversal of rotation of said grindingwheel.

13. A grinding machine comprising, in combination, means supporting aworkpiece for rotation and for translation in timed relation to therotation, drive means for said workpiece automatically operable toeffect reversal of said translation and timed reversal of rotation ofthe workpiece, a grinding spindle supporting a grinding wheel forcutting engagement with the workpiece in both directions of translationof the workpiece, drive means for rotating said spindle, and controlmeans for said drive means automatically operable upon reversal of saidwork translation and rotation to separate said wheel temporarily fromthe workpiece and during such separation to reverse the rotation of saidwheel.

14. A grinding machine comprising, in combiting engagement with theworkpiece in both directions of translation of the workpiece, drivemeans for rotating said spindle, and control means for,

said drive means automatically operable during said dwell period toseparate said wheel temporarily from the workpiece and during suchseparation to reverse the rotation of said wheel.

15. A method of grinding rotary workpieces comprising translating theworkpiece axiall in an initial direction and positively rotating theworkpiece in timed relation to the translation in an initial direction,rotating the grinding wheel in a predetermined initial direction whilein peripheral cutting engagement with the workpiece during the initialcutting stroke, stopping the translation of the workpiece with a dwellat the end of said' translation in the initial direction, reversing thedirection of rotation of the workpiece and of said grinding wheel duringsaid the grinding wheel.

16. A method of grinding rotary workpieces comprising translating theworkpiece axially in aseacce an initial direction and rotating theworkpiece in timed relation to the translation in an initial di.rection, rotating the grinding wheel in a predetermined initialdirection while in engagement with the workpiece during the initialcutting stroke, stopping the translation of the workpiece with a dwellat the end of said translation in the initial direction, retracting saidgrinding wheel from the workpiece during said 'dwell, reversing thedirection of rotation of the workpiece and of said grinding wheel duringsaid dwell, returning said grinding wheel into cutting position, andtranslating the workpiece axially in a return stroke through cuttingengagement with the grinding wheel.

17. A method of grinding rotary workpieces comprising translating theworkpiece axially in an initial direction and rotating the workpiece intimed relation to the translation in an initia1 direction, rotating thegrinding wheel in a predetermined initial direction while in engagementwith the workpiece, reversing the direction of rotation of the workpieceand of said grinding wheel at the end of said initial translation, andthen translating the workpiece axially in a return direction throughcutting engagement with the grinding wheel. I

18. A method of grinding rotary workpieces comprising translating theworkpiece axially in an initial direction and rotating the workpiece intimed relation to the translation in an initial direction, rotating thegrinding wheel in a predetermined initial direction while in engagementwith the workpiece, automatically reversing the 19. A grinding machinecomprising, in combin ation, means for supporting a workpiece for timedrotation-and translation in forward and return directions, a spindle forsupporting a grinding wheel mounted for cutting engagement with theworkpiece, and control means automatically operable upon translation ofsaid workpiece into a predetermined position to effect reversal in therotation of both the workpiece and the grinding wheel, said controlmeans including manual means selectively available at will to cause saidwheel to rotate either in the same direction or the opposite directionrelative to the direction of rotation of the workpiece.

20. A grinding machine comprising, in combin-' ation, means forsupporting a workpiece for timed rotation and translation in forward andreturn directions, drive means including a reversible hydraulic motorfor said workpiece and being automatically operated to effect reversalof said translation and timed reversal of the rotation of saidworkpiece, a spindle supporting a grinding wheel mounted for cuttingengagement with said workpiece, and electric control means automaticallyoperable upon translation or said workpiece into a predeterminedposition to enect substantial concurrent reversal in the rotation of theworkpiece and said grinding wheel. l

ALF KRISTIAN SELNES.

